Thoughts on Mollom + Alternatives

I recently moved a fairly popular site over to silverstripe. All good - but my spam on my forums went from zero in 4 years to a few comments per day Probably becuase my old system was hand writen, messy, and spammers just couldn't find it.

So I put Mollom on. Spam has stopped, but the number of real people signing up has also dropped off.